1. Field of the Invention
The present invention relates to an optical scanning device that performs optical writing in an electrophotographic-type printer or the like, and an image forming apparatus having the optical scanning device mounted thereon.
2. Description of the Related Art
Image forming apparatuses such as a laser beam printer, a digital copying machine, and a laser facsimile include an optical scanning device for writing a latent image on a photoconductor. Since high quality images are demanded of the image forming apparatuses in recent years, degradation of image quality due to interruption of laser beams, which is caused by adhesion of dust and dirt such as toner to a laser beam emitting unit, in the optical scanning device has been a major problem. In addition, with an increasing demand for downsizing of image forming apparatuses, arrangement of an optical write unit (an optical scanning device) in the image forming apparatuses has been diversified. In some cases, the optical write unit is arranged in a horizontal direction or below thereof, with respect to an image carrier of an imaging unit. In such a configuration, a dustproof glass provided at a laser beam emitting port is contaminated due to toner falling from the imaging unit or to dust and dirt scattering in the apparatus, thereby causing abnormality on formed images. Therefore, for example, in Japanese Patent Application Laid-Open No. 2000-263839, it is proposed to provide a shutter mechanism between an image carrier and an optical scanning device.
However, in the proposed technique, the shutter mechanism is arranged between the image carrier and the optical scanning device. Therefore, a space required in a vertical direction in an image forming apparatus increases, and the configuration contradicts with the downsizing demand accordingly.
Furthermore, in the apparatus described in Japanese Patent Application Laid-Open No. 2000-263839, since a gap between the shutter mechanism and the optical scanning device is large, toner and dust can enter from a lateral direction. Accordingly, degradation of the image quality cannot be sufficiently prevented.
Further, when the optical scanning device is arranged below the horizontal direction, there is a problem that dirt in the image forming apparatus is likely to adhere to a transparent member such as a dustproof glass provided on a light emitting window.
In addition, in recent image forming apparatuses, there is a trend that toners having a nearly spherical shape are used instead of ones with conventional shapes. However, the toners having the nearly spherical shape have a problem of cleanability, and cleaning of the toners by conventional techniques can be insufficient. With respect to this problem, for example, as in the technique of Japanese Patent Application Laid-Open No. 2000-263839, a shutter can be provided between the optical scanning device and the image carrier. However, since the shutter is open at the time of image formation, scattered dirt adheres to the dustproof glass.
Accordingly, since it is difficult to completely prevent degradation of image quality due to dirt only by a shutter, a cleaning unit needs to be provided separately. In this case, a configuration that combines the cleaning unit and the shutter is required.